It has long been a common practice in the well art to suspend an inner pipe, typically a casing string, concentrically within an outer pipe, typically an outer casing string or wellhead housing, by means of a hanger comprising a hanger member connected to the inner pipe and having a downwardly directed shoulder which engages an upwardly directed shoulder on the outer member as the inner pipe is run in. As the art developed, it became necessary to minimize the annular space between the inner and outer pipes and prior art workers have developed hangers employing a retractable hanger device carried by a mandrel on the inner pipe and capable of expanding into engagement with an outer hanger member when, as the inner pipe is run in, the mandrel reaches the outer hanger member. Such prior art hanger devices are disclosed in the following U.S. Pat. Nos.: 3,420,308 to Putch; 3,472,530 to Fowler; 3,592,489 to Baugh et al; 3,893,717 to Nelson; 3,918,747 to Putch; 4,073,511 to Haas et al; 4,167,970 and 4,181,331 to Cowan; and 4,232,889 to Putch.
However, as the search for oil in the offshore areas of the world increases, the depth of the offshore wells also increases. To withstand the pressures experienced at great depths, the apparatus used is larger and heavier. Unfortunately, many of the prior art hanger apparatus are not suitable for suspending the heavier pipes since they usually utilize only a single member to bear the load between the inner and outer pipes. Moreover, many of these prior art devices are complicated to manufacture and use and are not readily adapted to the increased demands of the heavier offshore equipment.